In July 2007, the Massachusetts State Highway Department (MassHighway) began paving a pavement rehabilitation project involving placement of HMA over a section of Portland cement concrete (PCC) pavement on Interstate 495. The pavement rehabilitation consisted of a 50.0mm (2 inches) thick Leveling Course, followed by a 25.0mm (1 inch) thick Reflective Crack Relief Interlayer (RCRI), and then overlaid with another 50.0mm (2 inches) thick intermediate course consisting of a dense-graded hot mix asphalt (HMA) mixture that was identical to the Leveling Course. Due to time constraints on the project, approximately 30% of the PCC had only received the initial 50.0mm (2 inches) thick Leveling Course by the end of the 2007 paving season, with the remaining lifts scheduled for placement over the PCC in the Spring of 2008. Within approximately two months after placement, reflective cracking was observed in the area where only the initial 50.0mm thick Leveling Course had been placed. Approximately six months after the section that included the RCRI had been placed, reflective cracking was also observed. This paper summarizes a field and laboratory forensic effort that was aimed at determining the cause of the early reflective cracking on Interstate 495 in Massachusetts. Field testing, consisting of Falling Weight Deflectometer and coring of PCC pavement, were used to assess the PCC joint performance in the vertical and horizontal deflection modes. Laboratory testing was conducted on laboratory prepared HMA and evaluated for cracking resistance under vertical and horizontal deflections and test temperaturesthat simulated field conditions. The results of the study clearly indicated that the dense-graded HMA mixture used as the Leveling and intermediate layers could not withstand the vertical and horizontal deflections of the PCC joints taking place on I-495. This paper also provides a general framework that can be used to assess the compatibility that different HMA mixtures may have with RCRI mixtures when intended for use in composite pavements, which can be utilized for mixture selection/design prior to field placement.
Samenvatting